The present invention pertains to devices and methods for facilitating bone fusion. The devices and methods disclosed can be used for fusion of joints. The invention is particularly advantageous for fusion of intervertebral joints.
Chronic back problems cause pain and disability for a large segment of the population. Frequently, the cause of back pain is traceable to diseased disc material between opposing vertebrae. When the disc material is diseased, the opposing vertebrae may be inadequately supported, resulting in persistent pain.
Surgical techniques have been developed to remove the diseased disc material and fuse the joint between opposing vertebral bodies. Stabilization and/or arthrodesis of the intervertebral joint can reduce the pain associated with movement of an intervertebral joint having diseased disc material. Generally, fusion techniques involve removal of the diseased disc and packing the void area with a suitable matrix for facilitating a bony union between the opposing vertebral bodies.
Surgical devices for facilitating interbody fusion have also been developed. These devices typically provide for maintaining appropriate intervertebral spacing and stabilization of the vertebrae during the fusion process. Examples of such devices are disclosed in, for example, U.S. Pat. Nos. 5,458,638, 5,489,307, 5,055,104, 5,026,373, 5,015,247, 4,961,740, 4,743,256 and 4,501,269, the entire disclosures of which are incorporated herein by reference.
Present methods for implanting a fusion device often require that the vertebrae be distracted to restore a diseased disc space to its normal height prior to implanting a fusion device In addition, the disc space is typically prepared for receiving an implant by drilling and tapping a bore of appropriate size for receiving the implant. Hence, current methods used for inserting presently available fusion implants require several steps and specialized instrumentation to prepare the implant site.
The time required to perform the steps for preparing the implant site prolongs the duration of the surgical procedure and thus, increases the duration of time that the patient is under general anesthesia. Also, the instrumentation used may require making a substantial skin incision. Furthermore, the steps used to distract and prepare the implant site increase the chance for trauma to neural, vascular and other tissues in the vicinity of the implant site.
Accordingly, there is a continuing need for improved intervertebral stabilizing devices and methods. The present invention is directed to addressing these needs.
The present invention is directed to an implant and methods for facilitating fusion of bone. The invention can be advantageously used in the stabilization and fusion of a joint, particularly an intervertebral joint. The invention helps to reduce the steps necessary for preparing the implant site and the time required for performing the overall implantation procedure. The invention also reduces the chance of injury to tissues near the surgical site.
It will be appreciated that throughout the specification, guidance may be provided through lists of examples. In each instance, the recited list serves only as a representative group. It is not meant, however, that the lists are exclusive.
An intervertebral fusion device according to the invention can have an expanded and a non-expanded configuration. The fusion devices have an internal surface, an external surface, a leading end and a trailing end. A portion of the external surfaces include an engagement arrangement to reduce the likelihood of movement or expulsion of the fusion device once implanted within the intervertebral space. The interior of the fusion devices can be packed with a bone support matrix to facilitate fusion between opposing bone surfaces.
The fusion devices each include an external member and an internal member. A portion of both the external and internal members can have a U-shaped configuration. The external member includes an external base and a first and second external side wall spaced apart by a width of the external base. The internal member also includes an internal base and a first and second internal wall spaced at an appropriate distance to permit the first and second internal walls to fit within the first and second external walls.
The fusion devices also include a locking arrangement. In general, a locking arrangement includes a pair of pins which interdigitate with a pair of apertures. In one embodiment, a first pin can project from the first internal wall and a second pin can project from the second internal wall. The first and second pins lock by interdigitating with a first and second aperture located on the first and second external walls respectively.
In an alternative embodiment, a first pin can project from the first external wall and the second pin can project from the second external wall. According to this embodiment, when locked in the deployed position, the first pin interdigitates with a first aperture located on the first internal wall and the second pin interdigitates with a second aperture located on the second internal wall. The invention describes various permutations of the relative positioning of the pins and the apertures to permit locking the fusion device in various expanded configurations. In some embodiments, the walls in which the apertures are located also include a groove to guide the pins into the aperture.
The invention also provides methods for implanting the fusion devices disclosed. In general, after preparation of the joint space, the leading end of the fusion device is inserted into the joint space and deployed into the expanded configuration. In addition to other advantages, the method disclosed can provide for reduced surgery time and reduced chance of trauma to tissues surrounding the joint space being fused.